Numerous polymer-based medical devices have been developed for the delivery of therapeutic agents to the body. For example, many state of the art medical devices consist of a device with a biostable or biodegradable polymeric coating that serves as the reservoir for one or more therapeutic agents. Ways to change the release rate of the therapeutic agent from the coating include changing the therapeutic agent loading, adding additional polymers (e.g., to change the hydrophilic/hydrophobic balance of the coating), the use of polymeric barrier layers, and so forth. Examples include drug eluting coronary stents, which are commercially available from Boston Scientific Corp. (TAXUS), Johnson & Johnson (CYPHER), and others.
Many types of polymeric materials have been used as the reservoir matrix into which the therapeutic agent is placed. Examples include polyisobutylene (PIB) based block copolymers, poly(butyl methacrylate), and poly(vinyl acetate), among others. It has been found that block copolymers based on polyisobutylene are particularly biostable and biocompatible, especially in the coronary artery which has been of particular interest for the development of drug eluting stents.
There is a continuing need for high performance polymeric materials that regulate the release of therapeutic agents, including those for use in medical devices.